Many people are affected by urinary incontinence. Incontinence is particularly common in the elderly; urinary incontinence is present in approximately fifty percent of nursing home patients, and urinary incontinence is a well known urologic problem in women. It will affect nearly all women in some form during their lifetime, and it is of significant social concern to all humans who experience it.
Urinary incontinence arises from the anatomy and the physiology of the urinary tract, which is composed of a bladder and a sphincter. Anatomically, the bladder consists of the bladder musculature, also known as detrusor, and the trigone. The sphincter includes the bladder neck and the proximal urethra. The detrusor muscle is innervated by the pelvic nerve through the parasympathetic nervous system, and the bladder neck and proximal urethra are innervated by the sympathetic nervous system.
The major functions of the bladder are the storage and expulsion of urine. The bladder is responsible for accommodating increasing volumes of urine at low pressures. Normally, the bladder remains closed during bladder filling and continence is maintained as long as the bladder neck and urethral pressure exceeds intravesical pressure. Voluntary voiding occurs when intravesical pressure exceeds bladder neck and urethral pressure, and involuntary voiding occurs when the intravesical pressure exceeds the bladder neck and urethral pressure.
Involuntary incontinence, also known as urge incontinence, occurs with a loss of a large volume of urine accompanied by symptoms of urgency, frequency and nocturia caused by an unstable bladder or detrusor instability. The patient may lose urine with a change in position or with auditory stimulation. The loss of small volumes of urine usually occurs because of bladder overdistension by a large amount of residual urine referred to as overflow incontinence.
The management of incontinence consists in administering a smooth muscle relaxant, such as oxybutynin, which acts directly on the smooth muscle at the site distal to the cholinergic receptor. The usual dose in the pharmacologic management is repeated doses from two-to-four times a day for oxybutynin. This is difficult to achieve as it requires rigid compliance and it is cost ineffective. Also, oxybutynin is adversely affected by light and it needs protection from air, which properties do not lend the drug to formulation into a dosage form that can administer oxybutynin at a controlled and known rate per unit time to produce the intended therapy.
In light of the above presentation it will be appreciated by those versed in the medical and pharmaceutical dispensing arts to which this invention pertains that a pressing need exists for a dosage form and for a therapeutic composition that can deliver the valuable drug oxybutynin in a controlled, extended dose to a patient in clinical need of incontinence management. The pressing need exits for an oral dosage form, for a therapeutic composition and for a method of therapy that can deliver oxybutynin at a controlled rate in a substantially constant dose per unit time for its beneficial therapeutic effect. The need exists further for a dosage form and a therapeutic composition that can deliver oxybutynin protected from light to insure that a complete dose of oxybutynin is administered to the patient and still remains substantially independent of the changing environment of the gastrointestinal tract. The need exists additionally for a sustained-release dosage form comprising the therapeutic composition that can deliver a therapeutic dose of oxybutynin for its intended effect, for avoiding an overdose, and for lessening the side effects that can accompany the drug. It will be appreciated further by those skilled in the dispensing art that if such a novel and unique dosage form, therapeutic composition and method are made available that can administer oxybutynin in a beneficial dose over time and simultaneously provide oxybutynin while lessening the incidence of both over and under dose, the dosage form, the therapeutic composition, and their accompanying methods would represent an advancement and a valuable contribution to the medical arts.